Aim 1. Structural analysis of HIV gp 120 complexes with candidate small molecules identified by other components of the program. Aim 2. Structural analysis of HIV gp 120 complexes with candidate miniproteins identified by other components of the program. Aim 3. Structural analysis of HIV gp120 complexes with CD4 D1D2 mutants and chemically modified derivatives of these mutant proteins to provide further insight into binding site characteristics. Aim 4. De novo design of small molecule mimetics of CD4 that can be synthesized for testing as gp120 ligands. Aim 5. Structural analysis of other relevant complexes such as those that bind to CD4 or DCSIGN to block interactions with HIV and those that block interactions between gp120 and chemokine receptors.